In recent years, the hybrid vehicle has been of interest as an environment-friendly vehicle. The hybrid vehicle is mounted with, in addition to a conventional engine, an electric motor supplied with electric power from a power storage device to generate a drive force for causing the vehicle to travel, and an electrical generator capable of charging the power storage device with electric power generated from an engine output.
A hybrid vehicle mounted with an electrical generator as described above and configured in such a manner that its power storage device is chargeable from a power supply outside the vehicle, like an electric vehicle without being mounted with an engine, is known (see, for example, Japanese Patent Laying-Open No. 08-037703).
Regarding the hybrid vehicle chargeable from an external power supply as disclosed in Japanese Patent Laying-Open No. 08-037703, the electrical energy can be supplied directly from the outside of the vehicle, so that the travel distance over which the vehicle can travel using only the motor while stopping the engine increases.
The amount of charge supplied to the hybrid vehicle from the outside of the vehicle can be increased to reduce the fuel consumption of the engine, so that the vehicle can travel in environment-friendly manner. In terms of the cost, while the fuel cost for the engine decreases, the cost for electric power necessary for charging increases and the load resulting from the charging is exerted on the power storage device to cause the power storage device to further degrade. The cost of using the power storage device therefore relatively increases.
On the contrary, if the amount of charge from the outside of the vehicle is decreased, the fuel consumption of the engine increases, so that the rate of contribution to the environment protection decreases. In terms of the cost, while the fuel cost for the engine increases, the cost of electric power necessary for charging decreases and the load on the power storage device accordingly decreases. Degradation of the power storage device is thus restrained. The cost of using the power storage device is therefore relatively decreases.
In order to further promote the prevalence of the electrically powered vehicle such as hybrid vehicle in the future, it is important to consider evaluation in terms of the cost as well as the environment. In particular, for the electrically powered vehicle chargeable from a power supply outside the vehicle, it is important to create a mechanism that can determine the amount of charge to the power storage device from a power supply outside the vehicle, in consideration of the cost of using the power storage device in addition to the energy cost.